Search for: All records

Vogelet al.reveals the stereochemical basis of alternative substrate cleavage byS. pyogenesSrtA for ligands with a P1′ Leu residue. The substrate adopts puckered alternative binding, whereby cleavage occurs between the P1′ and P2′ positions. 

The organic salt ( S )-nicotinium 2,6-dihydroxybenzoate undergoes reversible single crystal to single crystal phase transition at 104 K. The phase transition was monitored using temperature dependent single crystal X-ray diffraction and was attributed to symmetry breaking translations and rotations of the crystal components. 

In the title double proton-transfer salt, C 12 H 12 N 2 2+ ·2C 8 H 7 O 4 − , consisting of a 1:2 ratio of 4,4'-(ethene-1,2-diyl)dipyridinium cations ( trans bipyridinium ethylene) to 2-hydroxy-3-methoxybenzoate anions ( o -vanillate), the complete cation is generated by crystallographic inversion symmetry and it is linked to adjacent o -vanillate anions by N—H...O hydrogen bonds, forming trimolecular assemblies. The trimers are linked by C—H...O hydrogen bonds as well as aromatic π–π stacking interactions into a three-dimensional network. The anion features an intramolecular O—H...O hydrogen bond. 

ImportanceConsequences of subconcussive head impacts have been recognized, yet most studies to date have included small samples from a single site, used a unimodal approach, and lacked repeated testing. ObjectiveTo examine time-course changes in clinical (near point of convergence [NPC]) and brain-injury blood biomarkers (glial fibrillary acidic protein [GFAP], ubiquitin C-terminal hydrolase-L1 [UCH-L1], and neurofilament light [NF-L]) in adolescent football players and to test whether changes in the outcomes were associated with playing position, impact kinematics, and/or brain tissue strain. Design, Setting, and ParticipantsThis multisite, prospective cohort study included male high school football players aged 13 to 18 years at 4 high schools in the Midwest during the 2021 high school football season (preseason [July] and August 2 to November 19). ExposureA single football season. Main Outcomes and MeasuresThe main outcomes were NPC (a clinical oculomotor test) and serum levels of GFAP, UCH-L1, and NF-L. Participants’ head impact exposure (frequency and peak linear and rotational accelerations) was tracked using instrumented mouthguards, and maximum principal strain was computed to reflect brain tissue strain. Players’ neurological function was assessed at 5 time points (preseason, post–training camp, 2 in season, and postseason). ResultsNinety-nine male players contributed to the time-course analysis (mean [SD] age, 15.8 [1.1] years), but data from 6 players (6.1%) were excluded from the association analysis due to issues related to mouthguards. Thus, 93 players yielded 9498 head impacts in a season (mean [SD], 102 [113] impacts per player). There were time-course elevations in NPC and GFAP, UCH-L1, and NF-L levels. Compared with baseline, the NPC exhibited a significant elevation over time and peaked at postseason (2.21 cm; 95% CI, 1.80-2.63 cm;P < .001). Levels of GFAP and UCH-L1 increased by 25.6 pg/mL (95% CI, 17.6-33.6 pg/mL;P < .001) and 188.5 pg/mL (95% CI, 145.6-231.4 pg/mL;P < .001), respectively, later in the season. Levels of NF-L were elevated after the training camp (0.78 pg/mL; 95% CI, 0.14-1.41 pg/mL;P = .011) and midseason (0.55 pg/mL; 95% CI, 0.13-0.99 pg/mL;P = .006) but normalized by the end of the season. Changes in UCH-L1 levels were associated with maximum principal strain later in the season (0.052 pg/mL; 95% CI, 0.015-0.088 pg/mL;P = .007) and postseason (0.069 pg/mL; 95% CI, 0.031-0.106 pg/mL;P < .001). Conclusions and RelevanceThe study data suggest that adolescent football players exhibited impairments in oculomotor function and elevations in blood biomarker levels associated with astrocyte activation and neuronal injury throughout a season. Several years of follow-up are needed to examine the long-term effects of subconcussive head impacts in adolescent football players. 

Abstract A multivariate adiabatic connection (MAC) framework for describing dispersion interactions in a system consisting of N non-overlapping monomers is presented. By constraining the density to the physical ground-state density of the supersystem, the MAC enables a rigorous separation of induction and dispersion effects. The exact dispersion energy is obtained from the zero-temperature fluctuation–dissipation theorem and partitioned into increments corresponding to the interaction energy gained when an additional monomer is added to a K -monomer system. The total dispersion energy of an N -monomer system is independent of any partitioning into subsystems. This statement of dispersion size consistency is shown to be an exact constraint. The resulting additive separability of the dispersion energy results from multiplicative separability of the generalized screening factor defined as the inverse generalized dielectric function. Many-body perturbation theory (MBPT) is found to violate dispersion size-consistency because perturbative approximations to the generalized screening factor are nonseparable; on the other hand, random phase approximation-type methods produce separable generalized screening factors and therefore preserve dispersion size-consistency. This result further explains the previously observed increase in relative errors of MBPT for dispersion interactions as the system size increases. Implications for electronic structure theory and applications to supramolecular materials and condensed matter are discussed. 

1. The success of conservation initiatives often depends on the inclusion of diverse stakeholder interests in the decision-making process. Yet, there is a paucity of empirical knowledge concerning the factors that explain why stakeholders do—or do not—believe that they are meaningfully represented by government agencies. 2. Our study provides insight into the relationship between trust and stakeholder perceptions of inclusivity in public land management decisions. Here, we focus on the U.S. state of Alaska, where almost two-thirds of the land area are managed by the federal government. 3. We used structural equation modelling to test whether an individual's trust and the information sources used to learn about land management positively influenced perceived inclusivity. We conceptualized trust in terms of four dimensions that reflected an individual's disposition to trust, trust in the federal government, trust in shared values and trust that agencies adhere to a moral code. 4. We found that survey respondents across the U.S. state of Alaska had a limited disposition to trust others, did not trust federal land management agencies, did not believe agencies shared their values pertaining to protected area management and did not believe that agencies adhered to a moral code. 5. Beliefs about the morality of agencies were the primary driver of perceived inclusivity in land management decisions, indicating that agencies should focus on solving problems through deliberation and discussion about moral principles rather than by force. 6. Information acquired from professional, community-based or environmental advocacy exchanges also positively influenced perceived levels of involvement among stakeholders in resource management decisions. 7. These results provide a roadmap for how land management agencies can improve public relations and work towards a model of inclusive conservation around protected areas.